Although it is well established that structured documents and generic models bring benefits to applications involving documents, integrating these document models in the formatting process of interactive editors is still an open problem. In this paper, the problem of laying out and formatting structured documents is investigated, taking into account the DSSSL standard. One key point of this model is the possibility to express the logical structure of documents independently from their graphical aspect. However this approach induces a more complex formatting process, as two independent structures have to be merged. This discussion is illustrated by our experience of dynamic formatting in the Grif editor.